A device made of a moisture sensitive film or material laminated to a non-moisture-sensitive film or material can be used as an economical way to control humidity in a sealed package or confined space by reacting to the humidity level in the package and opening or closing a vent to outside air or to a desiccant sachet or moisture sink. As described herein, the level of humidity causes the valve to mechanically change shape and thus open or close an orifice. The control of humidity can extend the shelf life of packaged products and optimize the moisture content of products such as perishable foods or produce, medical products, electronic components, fine tobaccos and many other applications.
Targeting an optimal humidity level in a sealed package will become more critical with the increasing trend to design packaging to restrict air exchange to the minimum required Oxygen Transmission Rate (OTR).
For example, while packages restricting the OTR to reduce respiration rates and extend the shelf life of perishable foods are commonly used today, these packages also undesirably restrict the water vapor from venting out of the package.
Currently there is no attempt to control humidity independently from OTR in an OTR package for perishable foods or produce. Current packaging designs that address the issue of high humidity do so by creating large perforations “Macro perforations” or openings in the package. The inventor recognizes that perforations of this type cause the OTR to vent to the outside air. As such, this can negate any benefits of restricting OTR to extend shelf life of some perishable foods like produce and account for loss of weight of the produce being packaged. The large perforations also allows higher respiration rates and excess humidity to continually escape from the package, causing the humidity to go below the optimal level or undesirably drying out the perishable food.
Distributors and grocery stores address this loss of moisture and weight by controlling the atmospheric humidity, commonly by the use of water misters spaying water on the produce packaging. Water misters often create free standing water on the produce which in turn can generate water damage and or microbiological growth. Anti-fog films are used in produce packaging to prevent the appearance of condensation but do not prevent condensation itself or control the level of humidity.
The inventor believes that a buildup of moisture in a restricted OTR package will cause water damage due to condensation and microbiological growth. This may become the leading failure mode in packaged produce.
Also, in products measured by weight, weight reduction due to drying can effect the product's sale ability and accuracy of the product marking. By preventing the reduction of weight by keeping a constant humidity, the embodiments can avoid this issue.
The present application describes an OTR restriction and humidity control valve and package, and techniques for using these. These embodiments are well suited as a combined effort to extend the shelf life of perishable produce. Active humidity control will only be in effect under the conditions that it is needed.